The copyright law grants an author of an original work limited rights to assist the author in harvesting the rewards of his or her labor and creativity. These rights include the right to preclude others from reproducing and distributing the copyrighted work. Although both electronic and paper documents are copied by infringers, the ease with which electronic documents can be copied, edited and reproduced exacerbates the problem of providing evidence that an accused infringer has, in fact, copied the accused infringing work from the original work.
In some cases, the subject matter of the original work is new (e.g., a novel, a song, a painting) and evidence of copying can be shown by comparing the similarity between the original work and that of the accused infringing work. When, however, the subject matter underlying an original work is not new because it is in the public domain, the author may have difficulty providing evidence of copyright infringement because the original work and the accused infringing work should be similar (since both works are representative of the same underlying subject matter). Examples of original works whose underlying subject matter is in the public domain include, for example, a map of Virginia, a telephone directory of businesses in Arlington, a compilation of trigonometric tables, a compilation of government documents, etc.
Several techniques are used to help authors and publishers show copyright infringement in works whose underlying subject matter is not new. The first technique is commonly used by publishers of maps and involves "seeding" the map with errors. The theory being that if an accused infringer copies the original map, the infringer's map will contain the seeded errors, which it would not had the accused infringer created his or her map from original research. Similarly, the publishers of telephone directories and other compilations often seed their directories with fictitious entries, under the same theory. A problem with these approaches, however, is that they affect the fidelity of the original work.